CVE-2021-21640 in Jenkins
Summary
by MITRE • 04/07/2021
Jenkins 2.286 and earlier, LTS 2.277.1 and earlier does not properly check that a newly created view has an allowed name, allowing attackers with View/Create permission to create views with invalid or already-used names.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 04/11/2021
This vulnerability exists in Jenkins versions up to 2.286 and LTS versions up to 2.277.1 where the application fails to properly validate view names during creation processes. The flaw allows authenticated attackers who possess the View/Create permission to bypass name validation checks and create views with invalid or duplicate names. This represents a directory traversal and resource management issue that can lead to unauthorized access and system manipulation. The vulnerability stems from inadequate input validation within the view creation workflow, where the system does not enforce proper naming conventions or uniqueness constraints for view identifiers. According to CWE-20, this corresponds to improper input validation, while the ATT&CK framework categorizes this under privilege escalation and resource hijacking techniques. The issue specifically targets the Jenkins web interface and configuration management system, where view names are used to organize and access job information.
The operational impact of this vulnerability extends beyond simple naming conflicts as it enables attackers to potentially manipulate the Jenkins environment in ways that could disrupt normal operations. When attackers create views with invalid names, they may exploit parsing errors or injection points that could lead to further exploitation opportunities. The ability to create duplicate view names can cause confusion in the user interface, potentially leading to unauthorized access to jobs or resources that should be restricted. In multi-user environments, this vulnerability could allow attackers to overwrite existing views or create misleading navigation paths that hide critical information. The flaw particularly affects Jenkins administrators who rely on consistent view naming conventions for access control and operational management. The vulnerability creates a persistent threat vector that remains active as long as the affected Jenkins versions are deployed.
Mitigation strategies should focus on immediate patching of affected Jenkins installations to versions 2.287 and later where this vulnerability has been resolved. Organizations should implement additional access controls and monitoring around view creation activities, particularly for users with View/Create permissions. The recommended approach includes enabling audit logging for view creation events and implementing automated checks for duplicate or invalid view names. Security teams should review existing view configurations and remove any potentially malicious or duplicate views that may have been created. Network segmentation and principle of least privilege should be enforced to limit who can create views within the Jenkins environment. Regular security assessments should include verification of view name validation mechanisms and proper enforcement of naming conventions. The fix implemented in patched versions addresses the core validation logic by ensuring that new view names are properly checked against existing names and validated against acceptable patterns before creation. This aligns with security best practices for input sanitization and resource management as outlined in various security frameworks and standards.